Hydrocarbon production process



March 7, 1967 J. "r. KELLY ETAL 3,308,053

HYDROCARBON PRODUCTION PROCESS Filed Janv 19. 1965 Alkylafion 5 Reactor6 Cracker WAXY GAS OIL Hydroisom. Reactor INVENTORS JOE T KELLY BY ALANH. PETERSON GLEN CIEMPLEM N United StatesPatent P 3,308,053 HYDRQCAREGNPRODUCTIUN PRGCESS .loe T. Kelly and Alan H. Peterson, Littleton, Cola,and

Glen C. Templeman, Findlay, @hio, assignors to Marathan (iii Company,Findlay, Ohio, a corporation of (Thin Filed .lan. 19, 1965, Ser. No.426,583 11 Claims. (Cl. 208-67) under certain conditions,hydroisomerization of substantially straight-chain olefins containingfrom about 12 to about 16 carbon atoms with branched chain saturatedhydrocarbons having from 4 to about 6 carbon atoms in the moleculeproduces good yields of a hydrocarbon having an average of less thanabout 2 branches per molecule, useful as a jet engine fuel having lowpour point, high thermal stability, and high heat of combustion perpound. This hydroisomerization can also produce a coproduct fractionwhich is useful as a component in high octane gasoline.

A particularly unexpected feature of the new hydroisomerization reactionis its ability to produce the desired approximately singly branchedparaffinic hydrocarbons which are valuable as jet fuels when eithernormal or singly branched olefins are utilized as feed materials.

In the most preferred embodiment of the present invention, the olefinstarting materials are obtained by the molecular cracking of a waxy gasoil boiling above 600 F., under moderate conditions, to form a fractioncontaining from about C through C olefins for hydroisomerization, asecond fraction containing from about C through C olefins which isalkylated with branched chain saturated hydrocarbons to produce jetengine fuels, and a third fraction containing from about C through aboutC olefins which may be alkylated with isobutane or other low molecularweight isoparatfins to form a conventional alkylate gasoline. As aco-product where branched chain saturated hydrocarbons having from 4 toabout 6 carbon atoms are utilized in the hydroisomerization reaction, anadditional product component useful in the blending of high octanegasolines is obtained.

Thus the present invention in its most preferred embodiment permits theconversion of the low value waxy gas oil streams commonly found inpetroleum refineries to produce highly valuable jet engine and pistonengine fuels.

By waxy gas oil is meant any distillation cut boiling above about 600 F.of a virgin crude oil or refinery stream which contains an appreciableamount of parafiinic material. A particularly satisfactory waxy gas oilfor the purposes of this invention is obtained by distillation of whatare commonly called waxy crudes as opposed to less suitable asphalticcrudes.

The alkylation of isobutane with propylene, butylenes, and pentenes haslong been a commercial process for producing high octane gasolinestocks. This reaction exemplified below, has been studied extensively:

The product of the alkylation is, of course, a mixture of isomers ratherthan a single product as illustrated above. The reaction is normallycarried out in the pres- 33%,953 Patented. Mar. 7, 19.67

ence of concentrated sulfuric acid or anhydrous hydrofluoric acid with alarge excess (3 to 10 molars of isobutane over olefins to suppresspolymerization. The present invention in its most preferred embodimentmakes use of the above described conventional alkylation process as onestep in an integrated, coordinated series of reactions for thepreparation of engine fuels from low valued, high boiling petroleumstreams.

The hydroisomerization (hydrogen transfer) reactions utilized in theprocess of the present invention are typified by the reactionillustrated below:

As in the case of alkylation reactions, a variety of isomeric productsare formed. However, a surprising degree of specificity for methylundecanes and trimethylpentanes is exhibited by the above reaction.

The above reaction has been found to be general for isoparafiinsincluding, among others: isobutane, isopentane, and isohexanes and forsubstantially straight-chain olefins, preferably alpha-olefins in the C-C range. The singly branched paraffin products are eminently suited foruse as jet fuel for supersonic aircraft because of their good thermalstability, low freezing point, clean burning characteristics, andparticularly because of their high heat of combustion per pound. Whenisobutane is used as the isoparaffin, the gasoline boiling rangeco-product is of excellent octane quality and similar in composition toa conventional isobutane-butylene alkylate. The number of carbon atomsin the preferred isoparaflin may be varied somewhat in order tocompensate for variations in the average chain length of the C Cfraction and to optimize the properties of the gasoline and jet fuelproduced.

Pure normal alpha olefins are preferred as feed stocks for the presentinvention, but because they are more economically available, crudeolefins which have been separated into the proper carbon number rangesby distillation will frequently be employed. The olefins need not bepure straight-chain (normal) olefins because, as a peculiar and valuablefeature of the present invention, where a singly branched olefin isutilized in place of a preferred straight-chain olefin, the moleculewill usually be singly branched. The reaction of the invention favorsthe formation of singly branched hydrocarbons whether or not the olefinsused as raw materials are themselves branched. In general, it ispreferred that the olefins have an average of less than two branches permolecule.

It is not absolutely necessary that the double bond in the olefins occurin the preferred alpha position or that the olefin feed stock being fedto the hydroisomerization reactor be composed entirely of unsaturatedhydrocarbons. Substantial quantities of paraffinic hydrocarbons in thegeneral jet fuel boiling range may be tolerated without seriousinterference with the hydroisomerization reaction. It is important,however, that the quantity of normal paraflins in the olefin feedstocknot be sufiiciently high as to cause the fuel to have anunsatisfactorily high freezing point. Where necessary, excessive normalparrafiins may be removed in order to achieve a freezing point belowabout F., the preferred level for most jet fuels.

The hydroisomerization reaction of the present invention is preferablycarried out in a reactor equipped for efiicient mixing and with meansfor removing heat. The

conditions employed are similar to those normally practiced inisobutane-butylene alkylation. The preferred acid catalyst isapproximately 98% sulfuric acid but other concentrations of sulfuricacid, anhydrous hydrofluoric acid and other catalysts known to be usefulfor isobutane-butylene alkylation are useful in the hydroisomerizationreactions. These latter catalysts include among others various aluminumchloride complexes and boron trifiuoride complexes. The catalyst tohydrocarbon volume ratio is preferably between 2:1 and 01:1 and mostpreferably from about 1:1 to :1. Smaller amounts of catalyst may beemployed but the reaction times are then longer than those preferred forthe practice of the invention.

The drawing is a schematic illustration of a preferred embodiment of thepresent invention wherein the hydroisomerization reaction and thealkylation reactions are performed concurrently on different fractionsobtained from cracking of a waxy gas oil feedstock.

In the drawing waxy gas oil boiling within an approximate range of 600to 1000 F. is continuously passed through a thermal cracker. Spacevelocity through the thermal cracking unit is from about 0.2 to 6.0volumes per hour for each volume of internal capacity of the reactor,and is preferably from about 0.5 to about 2.0 volumes per hour. Thecracker operates at a temperature of from about 800 to 1200 F. andpreferably from about 1000 to 1100 F. A catalyst need not be employed,but where a catalyst is present, the temperature will preferably be fromabout 900 to about 1000 F. Suitable catalysts are those conventionallyused for the cracking of petroleum fractions including among others:silicaalumina,v activated alumina, and molecular sieves. Catalysts willin general tend to favor production of light olefins. The contact timewill be from about 1.0 to 50 and more preferably from to about seconds.Steam will be introduced into the cracking unit at a rate of about 1.5to about 10 and preferably from about 2.5 to 5 moles of steam per moleof feed.

The effluent from the thermal cracker consists predominantly of C toabout C olefins plus essentially unreacted gas oil. This efiluent is fedto a distillation tower 2, where it is split into four fractions; i.e.,a C C fraction which is utilized as gaseous fuel, chemical raw material,or any of the other uses to which such light hydrocarbon fractions arecommonly put such as alkylation of isobutane to form alkylate gasoline;a C -C fraction which is used further in the process of the presentinvention as discussed below; a (I -C fraction which is also hereafterdiscussed as being used in the process of v the present invention; and aC and above fraction which may be further distilled and partiallyrecycled to the thermal cracking unit. The C to C fraction fiows througha mixing T, or hatch-type mixingdevice 3 where it is mixed withisobutane or one of the other suitable paraflin fractions discussedpreviously. The mixture of the isoparafi'in with the C C olefins fromthe cracking unit then flows into the alkylation reactor 4 whichoperates at a temperature of about 30 to 60 P. if sulfuric acid is usedas the catalyst or alternatively at from about 4 to about 140 P. ifanhydrous hydrogen fluoride is used as a catalyst. In either case thecatalyst to hydrocarbon volume ratio is from about 2:1 to 0.111 or morepreferably from 1:1 to 0.221. The isoparafiin in the input to thealkylation reactor will be in the range of from 2 to 100 and preferablyfrom 4 to about 10 moles of isoparaffin per mole of olefin, thesubstantial excess being employed to minimize polymerization.

Contact time in the alkylation reactor will be from about 1 to about 120minutes with contact times of 5 to 30 minutes being preferred.

The efiluent from the alkylation reactor is sent through separator 5where unreacteed isobutane is separated out and recycled back to themixer 3. The remainder of the etiiuent is transferred to fractional dis-4 tillation column 6 where a gasoline fraction composed primarily of C Chydrocarbons boiling from about 82 to 350 F., and a jet fuel fractioncomposed principally of C -C hydrocarbons boiling from about 350 to 550F. The fractions are separated and sent to storage units for gasoline 7and for jet fuel 8.

The C -C hydrocarbon fraction from the distillation column 2 flowsthrough a mixer 9 where it is mixed with from 2 to about 100 andpreferably from 4 to about 10 moles of isoparafiin per mole of G -Colefin. The isoparafiins fed into the mixer will be from C -C withisobutane being preferred in most instances.

The mixed (I -C olefin/isoparaffin efiiuent from the mixer flows intothe hydroisomerization reactor 10 which operates at conditions generallysimilar to those under which the alkylation reactor operates. Thetemperature for the hydroisomerization reaction is from about 30 to 100and preferably from to 90 F. The pressure is from about 0 to 500 andpreferably the vapor pressure of the reactants. The catalyst ispreferably sulfuric acid but hydrofluoric acid or other catalysts may beused. The volume ratio of catalyst to total hydrocarbon in the reactoris maintained at about 2:1 to 01:1 and preferably from about 1:1 to0.2: 1. The concentration of the H 50 used is about to 105% by weightwith 85 to 100% preferred and to 99% by weight especially preferred.Where hydrogen fluoride is used as the catalyst, the temperature rangewill be from about 4 to about 140 F. The contact time will be maintainedat from about 1 to 120 and preferably from about 5 to 30 minutes.

The effluent from the hydroisomerization reactor is sent to separationzone 11 where the unreacted isoparaffins are separated out and recycledback to the mixer 9. The remainder of the product of thehydroisomerization flows to a conventional fractional distillationcolumn 12 where a gasoline fraction consisting primarily of C to Chydrocarbons boiling in the range of 82 to 350 F. and a jet fuelfraction consisting primarily of C -C singly branched paraffinichydrocarbons boiling in the range of 350 to 550 F., are separated. Thegasoline fraction may be transferred to storage facility 7 to be mixedwith the corresponding fraction from the alkylation efiiuent, or storedseparately and the jet fuel fraction may be similarly sent to storagefacility 8 to be blended with the corresponding fraction from thealkylation effluent or stored separately.

It should be understood that although the above de scribed embodiment ofthe present invention utilized thermal cracking of waxy gas oils withsteam, the product of suitable cracking operations according toconventional techniques and olefins obtained from such thermally crackedstreams as coker distillates and visbreaker sidecuts or naphthas willalso be useful in the practice of the present invention. Also, it willbe recognized that the novel hydroisomerization process of the presentinvention can be practiced with approximately C -C olefins (preferablyalpha unsaturated) which are obtained from other sources.

Example I A waxy gas oil boiling above 600 F. is cracked with steam at1,150 P. in a laboratory size thermal cracker. No catalyst is used inthe cracking step. Oil is fed at the rate of 452 g. per hour and steamat 202 g. per hour into the cracking unit with a retention time of 0.33second. In a single pass, a 28.1 weight percent conversion is ob tained.The products are separated by distillation into cuts as follows: Cthrough 44.5 weight percent; C through C 15.5 weight percent consistingcompletely of olefins; C through C 20.5 weight percent and olefins, andC C 16.9 weight percent containing 92% olefins.

The C to C cut is hydroisomerized using isobutane as the hydrogen sourceto produce a premium quality jet fuel and a high octane gasolineblending component. The by droisomerization is carried out in anautoclave with 99 weight percent sulfuric acid as a catalyst. Thecatalyst to olefin weight ratio is 5.0 and the isobutane to olefin moleratio is 10.0. The olefin is pumped into the reactor containing theother reactants over a period of about 20 minutes and the reactionmixture is stirred for 5 minutes at the reaction temperature of 40 C.The yields obtained in the hydroisomerization reaction are gasoline,which has a boiling point to 350 F., 28 weight percent; jet fuel, whichhas a boiling point range from about 350 F. to 500 F., 64 weightpercent; and alkylate plus polymer, which has a boiling point above 500F., 8 weight percent. The fraction boiling above 500 F. is suitable forsale as fuel oil.

The C to C cut is converted to high quality jet fuel by alkylation withisobutane using anhydrous hydrogen fluoride as the catalyst. Thisreaction is carried out in a Monel autoclave using a catalyst to olefinWeight ratio of 5:1 and an isobutane to olefin mole ratio of 10:1. Thealkylation reaction is run at 2 to 4 C. Addition of the olefin to thereactor containing the other reactants requires minutes. The reactionmixture is stirred for an additional 20 minutes to complete thereaction. Yields based on weight of olefin fed are gasoline (liquid to350 F.) 50 weight percent, jet fuel (350 F. to 500 F.) 70 weightpercent, and polymer (above 500 F.) 10 weight percent.

The jet fuel fraction obtained by the hydroisomerization has an averageof 3.1 methyl groups (1.1 branches) per molecule and that obtained byalkylation has an average of 3.5 methyl groups (1.5 branches) permolecule. This low degree of branching is indicative of good thermalstability.

Example 11 When similar cracked waxy gas oil products arehydroisomerized using substantially anhydrous HF (containing less than2% water by weight) at a temperature of about 50 0, products and yieldsare approximately as in Example I.

What is claimed is:

1. A process for the conversion of a waxy gas oil to valuable enginefuel comprising molecularly cracking under moderate conditions to obtaina product comprising substantial amounts of olefins having from about 6to about 16 carbon atoms, separating a fraction containing from about 12to about 16 carbon atoms per molecule, hydroisomerizing said fraction atfrom 20 to 80 C. in the presence of an acid catalyst with an isoparaffinof 4 to about 6 carbon atoms as the hydrogen source to form a gasolinefraction having a boiling point below about 350 F., a jet fuel fractionhaving a boiling point of from about 350 to 550 F., and a higher boilingfraction having a boiling point above 550 F.; separating out anapproximately C to C fraction from the product of said molecularcracking, alkylating said C C fraction with a branched chain hydrocarboncontaining 4 to about 6 6 carbon atoms in the presence of an acidcatalyst at from 20 to C. to obtain a gasoline fraction boiling belowabout 350 F., a jet fuel fraction boiling from about 350 to 550 F., anda high boiling fraction boiling above 550 F.

2. The process of claim 1 wherein the branched chain hydrocarbon isisobutane, and the olefins are 6 to 16 carbon atom alpha-unsaturatedolefins.

3. A process for the manufacture of acyclic branched hydrocarbons withan average of less than two branches per molecule having relatively highthermal stability, low freezing point, high heat of combustion perpound, and boliing from about 300 to 550 F., comprising hydroisomerizingsubstantially straight-chain olefins having from 9 to about 16 carbonatoms per molecule with isoparafiins having from 4 to 6 carbon atoms permolecule in the presence of an acid catalyst selected from the groupconsisting of sulfuric acid and hydrogen fluoride, aluminum chloride andboron trifluoride at a temperature of about 20 to 80 C. to produceisoparafifins of the same number of carbon atoms as the olefins togetherwith more highly branched paraflins containing twice the number ofcarbon atoms of the isoparaffins.

4. The process of claim 1 wherein the acid catalyst is selected from thegroup consisting of to about by weight H 80; and substantially anhydroushydrogen fluoride.

5. The process of claim 1 wherein the acid catalyst is 85 to 100% byweight H 50 6. The process of claim 5 wherein the branched chainhydrocarbon is isobutane, and the olefins are 6 to 16 carbon atomssubstantially alpha-unsaturated olefins.

7. The process of claim 6 wherein the gasoline fraction obtained fromthe hydroisomerization is blended with the gasoline fraction obtainedfrom the alkylation and the jet fuel fraction obtained from thehydroisomerization is blended with the jet fuel fraction obtained fromthe alkylation.

8. The process of claim 3 wherein the acid catalyst is 85 to 100% byweight H 50 9. The process of claim 3 wherein the acid catalyst ishydrogen fluoride.

10. The process of claim 3 wherein the acid catalyst is aluminumchloride.

11. The process of claim 3 wherein the acid catalyst is borontrifluoride.

References Cited by the Examiner UNITED STATES PATENTS 2,172,228 9/1939Van Paski 208-106 2,353,490 7/1944 Noorduyn 20871 2,391,415 12/1945Grosse et a1. 260-68348 3,150,204 9/1964 Lawley et al 260683.59

DELBERT E. GANTZ, Primary Examiner.

ABRAHAM RIMENS, Examiner.

1. A PROCESS FOR THE CONVERSION OF A WAXY GAS OIL TO VALUABLE ENGINEFUEL COMPRISING MOLECULARLY CRACKING UNDER MODERATE CONDITIONS TO OBTAINA PRODUCT COMPRISING SUBSTANTIAL AMOUNTS OF OLEFINS HAVING FROM ABOUT 6TO ABOUT 16 CARBON ATOMS, SEPARATING A FRACTION CONTAINING FROM ABOUT 12TO ABOUT 16 CARBON ATOMS PER MOLECULE, HYDROISOMERIZING SAID FRACTION ATFROM -20 TO 80*C. IN THE PRESENCE OF AN ACID CATALYST WITH ANISOPARAFFIN OF 4 TO ABOUT 6 CARBON ATOMS AS THE HYDROGEN SOURCE TO FORMA GASOLINE FRACTION HAVING A BOILING POINT BELOW ABOUT 350*F., A JETFUEL FRACTION HAVING A BOILING POINT OF FROM ABOUT 350 TO 550*F., AND AHIGHER BOILING FRACTION HAVING A BOILING POINT ABOVE 550*F.; SEPARATINGOUT AN APPROXIMATELY C7 TO C11 FRACTION FROM THE PRODUCT OF SAIDMOLECULAR CRACKING, ALKYLATING SAID C7-C11 FRACTION WITH A BRANCHEDCHAIN HYDROCARBON CONTAINING 4 TO ABOUT 6 CARBON ATOMS IN THE PRESENCEOF AN ACID CATALYST AT FROM -20 TO 80*C. TO OBTAIN A GASOLINE FRACTIONBOILING BELOW ABOUT 350*F., A FET FUEL FRACTION BOILING FROM ABOUT 350TO 550*F., AND A HIGH BOILING FRACTION BOILING ABOVE 550*F.